The OSADL OPC UA/TSN Project

Rationale

State of the art

The Ethernet standard and the future evolution of this base communication layer represents today an important standard of interoperable network communication - in fact from sensor via control system up to the server. According to common understanding, this will remain so without doubt in the near and even less near future. To the contrary, there are many doubts that the upper communication layers will remain as they are now, since the desired deterministic and interoperable connectivity of the future requires that only a single protocol be used - instead of the more than 40 different ones none of which has reached more than 50 percent market share. In addition, communication methods are needed that require much less resources than today which is an important prerequisite to serve the expected large number of future nodes.

Next generation OPC UA

In order to obtain the mentioned interoperable connectivity, it was proposed some time ago to equip the already existing OPC UA protocol with additional features needed by industry and establish it as a unified communication protocol of the future. OPC UA runs even on systems that provide only a minimum of resources with respect to network bandwidth and computing power. Deterministic communication via this protocol shall be obtained using Time Sensitive Networking (TSN) that currently undergoes standardization. Two important protocol additions needed by industry that also are about to be standardized are Publish ("Pub") and Subscribe ("Sub"). While the former is needed to simultaneously send messages to a number of receivers, the latter allows a program component to register for a particular event such as sensor data exceeding or falling below permissible limits to avoid polling.

Project phase #1

In addition to the standardization of the protocols, to gain general acceptance of this technology it also is necessary to provide a freely accessible software implementation that can be used in an unrestricted way. Since this currently is not not the case, the Open Source Automation Development Lab (OSADL) in collaboration with Indian system integrator Kalycito Infotech has launched a related Open Source software project that is funded by Kalycito and an OSADL project group. The already developed and further to be enhanced software is based on the OPC UA implementation that was created in the open62541 project (https://open62541.org/). The Fraunhofer Institute of Optronics, System Technologies and Image Processing (Fraunhofer IOSB) has taken over the activity of programming the OPC UA enhancements; this was a logical decision, since Fraunhofer IOSB already played an important role in the development of the original open62541 project.

Demonstrator at Embedded World 2018

Flyer distributed at the OSADL booth of the Embedded World 2018

The currently available results of the named project will be presented at the OSADL booth of Embedded World 2018 (hall 4, booth 168) in a demonstrator with several TSN nodes and concurrent real-time and non-real-time communication. The demonstrator contains a variety of TSN hardware and software implementations of various vendors that communicate to each other using a unified OPC UA implementation and provides the following features for the first time under an Open Source license that can be used in proprietary products:

Brokerless OPC UA Pub/Sub via IP multicast and the binary message encoding format according to draft of part 14 of the OPC UA specification

Integration of the publisher in a regular OPC UA server with additional real-time interrupting

Implementation of the subscribers as standalone software

Hardware

Intel Atom/I210 by TQ-Systems

FPGA-TSN by Analog Devices

FPGA-TSN Cyclone V SoC by Intel/Altera

FPGA-TSN Zync SoC by Xilinx

Software development and project management

Fraunhofer IOSB

Kalycito Infotech

Open Source Automation Development Lab (OSADL)

Partial funding and other contributions through the following participants of the OSADL project

Heidelberger Druckmaschinen

Kontron

Linutronix

Pilz

SICK

TQ-Systems

Letter of Intent (project phase #1)

Project phase #2

After the successful completion of the above described project phase #1, there is now an OPC UA implementation available that can be used by industry with rich generic features ready to be combined with a proprietary technology and application to deliver tangible outcomes to customers. In parallel to the project phase #1, patches for the Linux kernel were made available to use a PTP synchronized link for time based packet submission. A test link is now part of the OSADL QA farm where the synchronization quality of the PTP link is monitored continuously.

While a very affordable total cost of ownership is a key differentiator of this joint initiative, the market demands longevity, maturity and commercial support alongside such a program. It, thus, is the aim of this Letter of Intent of project phase #2 to launch a subsequent community project that fills the gap to use the existing OPC UA PubSub over TSN software components in real products and release them to the industry and automation market.